This invention relates to magnetic resonance imaging, and more particularly to local coils for imaging specific anatomical features of a patient.
Magnetic resonance imaging is a common modality used to image different portions of a patient's anatomy. In doing so, the patient is placed in a strong uniform magnetic field to polarize nuclei within the cells of the patient causing the nuclei to precess at their characteristic Larmor frequency. By applying another excitation magnetic field near the larmor frequency, the precessing nuclei become aligned. The signals emitted at the Larmor frequency by the precessing nuclei when the excitation field is removed are detected and employed to create an image of the internal anatomy of the patient.
The basic magnetic resonance imaging system utilizes coils which enclose substantially the entire body of the patient and excite the nuclei within that portion. When only a specific section of the patient's body is desired to be imaged, a smaller radio frequency coil often is used to excite the nuclei and to receive the signals emitted by the nuclei thereafter. Such smaller coils are often referred to as local coils, and a variety of them have been designed specifically to image the spine, abdomen, extremities and other body regions.
Although most of the MRI imaging was performed for diagnostic purposes, it is desirable to be able to perform magnetic resonance imaging during surgical procedures. During such procedures, a detailed image of the region of exploration is created using the magnetic resonance system to guide the manipulation of instruments by the surgeon. However, the structure of conventional coils made it impractical to cut holes through the coil to gain access to the patient's anatomy. In addition, the introduction of other equipment into a full body coil can interfere with the excitation of the nuclei and the reception of their emitted signals. Heretofore, the local coils designed for specific parts of the patient's anatomy were rigid structures and did not permit access to that portion by surgical instruments.